Alternate action mechanism

ABSTRACT

The present invention relates to a new improved alternate action mechanism for control devices, such as switches, which utilizes a pawl mounted for free rotation on an actuator and for operative association with camming surfaces formed in an associated hollow casing. The camming surfaces act to partially rotate the pawl on an initial downward stroke of the actuator to such an extent that the pawl cooperates with the camming surfaces to preclude total return of the actuator without subsequent reciprocal motion of the actuator further rotating the pawl. Contiguous opposite sides of a pawl tooth are engaged by a shoulder portion of said camming surfaces to prevent return.

United States Patent Elliott 51 Sept. 12, 1972 [54] ALTERNATE ACTIONMECHANISM 22 Filed: March 19,1971

211 Appl.No.: 126,162

[52] US. Cl. ..200/153 J [51] Int. Cl. ..l-10lh 13/56 [58] Field ofSearch ..200/153 J, 169 PB [56] References Cited UNITED STATES PATENTS3,165,612 1/1965 Bailey ..200/153 UX J 3,153,714 10/1964 Bury ..200/153J3,148,255 9/1964 Myrent et al ..200/153 J FOREIGN PATENTS ORAPPLICATIONS 1,171,778 11/1969 Great Britain ..200/153 J PrimaryExaminer-David Smith, Jr.

Assistant Examiner-Robert A. Vanderhye Att0meyRobert W. Beart, Jack R.l-lalvorsen, Thomas W. Buckman and Edward L. Benno 57 ABSTRACT Thepresent invention relates to a new improved alternate action mechanismfor control devices, such as switches, which utilizes a pawl mounted forfree rota tion on an actuator and for operative association with cammingsurfaces formed in an associated hollow casing. The camming surfaces actto partially rotate the pawl on an initial downward stroke of theactuator to such an extent that the pawl cooperates with the cammingsurfaces to preclude total return of the actuator without subsequentreciprocal motion of the actuator further rotating the pawl. Contiguousopposite sides of a pawl tooth are engaged by a shoulder portion of saidcamming surfaces to prevent return.

6 Claims, 5 Drawing Figures llllillllllllllllll Illlllllllllllllilllllllllllll ALTERNATE ACTION MECHANISM Many new innovations have beendeveloped in the electrical control field which have advanced the stateof the art to a high level. In one area of this field, repetitiveactuator and re-ease mechanisms, more commonly known as alternate actionmechanisms, have been developed for actuating a control device andmaintaining the same in either of two positions when operated. Suchmechanisms provide alternate operation of a switch where controlled bysuccessive actuations of an operator, such as a plunger, push button orthe like.

The various configurations of the prior art alternate action mechanismsgenerally require a relatively longreset stroke and quite often do notlend themselves to true and positive resetting without repeatedmovements of the actuator.

Accordingly, it is an object of this invention to provide an alternateaction mechanism which is reliable and provides a positive uninterruptedaction.

A further object of this invention is to provide an alternate actionmechanism which requires a short reset stroke following the actuatingstroke.

Yet another object of the present invention is a provision of analternate action mechanism which is relatively simple and inexpensiveand yet has a strong and rigid construction.

Still a furtherobject of the present invention is the provision of a newand improved alternate action mechanism which can be utilized withavariety of switch mechanisms. I

The above stated and other objects of the invention are accomplished bythe provision of an actuator keystem mounted in a hollow casing forreciprocal movement therein. A freely rotatable pawl is mounted on thekeystem for association with a plurality of camming surfaces which actto alternately restrict movement of the actuator toward its initialposition and allow the actuator to resume its initial position.

Other objects and advantages will become apparent from the followingdescription when taken in connection with the accompanying drawingswherein:

FIG. 1 is an exploded view of a key switch including the new alternateaction mechanism.

FIG. 2 is a front view of the switch in its normal or undepressedcondition.

FIG. 3 is a sectional side view taken along the line 3-3 of FIG. 2.

FIG. 4 is an enlarged fragmentary view of the pawl and camming surfacesof the alternate action mechanism.

FIG. 5 is a side elevation view of the pawl member.

FIGS. 1 through 3 illustrate a preferred embodiment of the inventioncomprising a housing or guide support means 10, a magnetic core 12,first and second permanent magnets 14 and 16, a keystem l8 and a keystemreturn spring 20. A keycap 22 is attached to the top of the keystem. Thecore 12 and permanent magnets 14 and 16 comprise the switching mechanismparticularly shown and claimed in co-pending, commonly assignedapplication, Ser. No. 879,220 filed Nov. 24, 1969 which on Aug. 16,1971, issued as US. Pat. No. 3,638,221. The particular details of theswitches are not important to the invention and it should be understoodthat a variety of mechanical switching mechanisms can be utilized inlieu of the magnetic switching mechanism, without departing from theinvention.

The housing is an elongated body which may be square and need be nowider than the dimensions of the keycap. The housing may be formed withan overhanging ledge portion 100 extending partially around this top, Aportion of two opposing sides of the housing are formed at an angle tothe length of the housing so as to provide two cars 1011. The cars 10bhave a certain degree of resiliency so that the switch housing may beinserted downwardly through a hole in a support plate 24 as shown inFIG. 2. After the ears pass through the hole, they expand outwardly toprevent upward movement of the housing. The ledge 10a prevents downwardmovement. Thus the housing may be firmly locked in position in thesupport plate. If necessary, the housing may be removed from the plateby pressing the ears inwardly and lifting the housing. The housing has alongitudinal opening 11 for receiving the keystem 18 which, as shown inFIG. 1, is a generally box like structure having two legs 18a and 18b. Acentral portion 10c of the housing extends from one side of the housingto the other, thus bisecting the lower portion of the opening 11. A post10d extends upwardly from the central portion 100 to retain acompression spring 20 which is compressed between portion 100 of thehousing and the underside of the tip portion of the keystem 18.

The lower portion of the housing 10 is formed so as to have a recess l0eextending across it between opposite sides. A further recess is formedperpendicular to recess 10c and extending through the central portion10c of the housing. A ferrite toroidal core 12 is positioned in thefurther recess so that its center opening is aligned with recess 102. Asshown in FIG. 3, this arrangement locates the core 12 so that it may bereadily threaded by one or more windings 26. The core may be force fitinto the recess or held in place by a suitable adhesive material. Thelegs 18a and 18b of the keystem are punched to form tangs 18e which holdpermanent magnets 14 and 16. When the switch is in the depressedstatethe permanent magnets are moved away from the core 12 and the coredesaturates. The particular switching mechanism thus described canreadily be exchanged with snap action switching mechanisms as describedin US. Pat. No. 3,300,611 or other switching mechanisms withoutdeparting from the scope of this invention.

As shown in FIG. 1, the keystem actuator 18 carries a pawl 29 which maybe snapped in an aperture in leg 18a for free rotation therewith. Thepawl is in registry with an aperture 28 formed in one side of the casing10.

The aperture 28 in combination with the pawl 29 provides a reliablealternate action switching mechanism as will be set forth below. Theaperture is of an irregular shape and includes a plurality of cammingsurfaces 30, 32, 34, 35, 36, 37, 38, 40, 42, 44, and 46 as shown in FIG.4.

The pawl 29 is formed in a generally trapezoidal shape having a pair ofshort sides 48 and a pair of long sides 50. The trapezoidal shaped pawlincludes a pair of acute angles A forming relatively sharp teeth 52 atjunctures of sides 48 and 50. The remaining junctures of sides 48 and 50are formed in a generally obtuse included angle and are relativelysmooth surfaces.

FIG. 2 shows the cam and actuator in an initial position biasedoutwardly as a result of spring 20. In the initial position of the pawl,as seen in FIG. 2, the long side 50 of the pawl, and surface 30 of theaperture extend in planes generally parallel to a longitudinal axis ofthe keystem 18, which longitudinal axis may also be used to describe theorientation of the aperture with the casing and the keystem. Theaperture 28 is arranged relative to the pivot point of the pawl so as toposition a long side 50 closely adjacent to a side support surface 30which tends to orient the pawl along the above mentioned longitudinalaxis of the actuator. It should also be noted that the angle formed bythe intersection of surfaces 30 and 46 is preferably equal to angle Athus additionally serving to orient the pawl 29 within the aperture 28.j

The aperture 28 includes a pocket-like portion formed from the surfaces38 and 40. Likewise a first shoulder-like portion is formed fromsurfaces 32 and 34. FIG. 4 further shows a second shoulder-like portionformed from surfaces 40 and 42. The importance of these portions inconjunction with the particular configuration of the pawl will beapparent in the following detailed description of the operation of thedevice.

A description of the consecutive positioning of the pawl will beclarified by the use of suffixes a through d when referring to fourbasic positions of the mechanism.

As the actuator begins a downward stroke, the pawl 29 remains inalignment with the longitudinal axis of the actuator as a result of thesupport surface 30. At the lowermost portion of the downward stroke theteeth 52a contact rotation inducing surface 38 in the pocket whichforces the pawl out of axial alignment with the longitudinal axis.Rotation limiting surface 40 of the pocket restricts this rotation tothat of a predetermined extent. It should be noted that the particularangular relationship of the rotation inducing ramp 38 with a horizontalaxis, in conjunction with acute angle A of the pawl insures that thisrotation takes place. The complement of the angle A is shown to begreater than the angle B defined by a horizontal plane and ramp surface38. An example of values of these respective angles which has been foundto be adequate in actual operation are approximately 54 for angle A and30 for angle B.

After the pawl and actuator reach the bottommost portion of the aperture28, the biasing means acts to force the actuator to return to itsinitial position. However, as a result of the partial rotation of thepawl, tooth 52b is now aligned with a shoulder portion formed fromsurfaces 32 and 34. This shoulder portion retains the pawl from furtherrotation and further upward movement of the actuator. Thus the actuatoris held from releasing the switch mechanism. The switch mechanism isreleased by subsequent movement of the keystem actuator against the biasof the return spring 20. This further reciprocation of the keystemresults in tooth 52c abutting a second shoulder means formed fromsurface 42 and 40. This shoulder means further rotates the pawl as aresult of the camming action of side 48 on surface 42. The furtherrotation places tooth 52d out of alignment with the first shoulderportion 32, 34 and brings tooth 52d into alignment for subsequentcontact with a surface 35. As a result of the bias of the return springand the camming action of tooth 52d on surface 35, the pawl is rotatedfurther in the upward stroke of the actuator and eventually assumes aposition 180 from the initial position. The initial orientation isachieved as a result of the aforementioned surfaces 30 and 46.

The axial distance between the surfaces 32 and 42 is slightly largerthan the length of the longer side 50. It will be apparent that thisrelationship results in an extremely short reset stroke. The sharpcorners of the teeth 52 aid in properly seating and locking the pawl inthe shoulder 32 and 34, which are similarly joined in a sharp angularrelationship.

A further embodiment of the invention includes a sharp projection 54 onsurface 32 of the first shoulder means which presents a slightinterference in the seating of the pawl and presents a snap-like feel tothe actuator.

From the forgoing, it will now be apparent that the present inventioncontemplates a novel and unique alternate action mechanism capable ofbeing moved quickly from an at rest to a latched position and back againutilizing a relatively short reset stroke. The positive lock and thecapability of use for many switching mechanisms makes the instantalternate action mechanism desirable for many commercial applications.While the preferred embodiment of the present invention has been shownand described herein, it is obvious that many structural details may bechanged without departing from the spirit and scope of the appendedclaims.

lclaim:

1. An alternate action mechanism comprising, in combination a hollowcasing, a switch actuator mounted in the casing for straight linereciprocating movement therein, means biasing the actuator in a firstdirection, switch means operatively associated with the actuator, pawlmeans carried for free rotation on the actuator, an aperture in thehollow casing forming camming surfaces and arranged for operativeassociation with the pawl means, said pawl means comprising a pawlmember having a pair of teeth on the opposite ends thereof, the cammingsurfaces comprising pocket and shoulder portions, the pocket portionpositioned to engage one of said teeth when said pawl member is in aninitial position and partially rotate said pawl member responsive tomovement of the actuator in a direction opposite to the bias, theshoulder portion formed and positioned to lockingly engage contiguousopposite sides of the second tooth of said pawl member to preclude thereturn of the actuator to its initial position responsive to saidpartial rotation of said pawl member, a second shoulder portionpositioned to engage said one of said teeth and further rotate said pawlresponsive to a second movement of the actuator in a direction oppositeto the bias, and said camming surfaces including a further surfaceengaging and rotating said pawl member to an initial position responsiveto further movement of the actuator in the direction of said bias.

2. An alternate action mechanism in accordance with claim 1 wherein thecamming surface is in the form of an aperture in one wall of the hollowcasing and said further surface comprises a side support surfaceextending from the uppermost portion of the aperture in a planegenerally parallel to the plane including the longitudinal axis of theactuator, the pocket portion forming the lowermost extremity of theaperture and including a rotation inducting ramp surface and a rotationlimiting abutment surface wherein the side support surface axiallyaligns the pawl member within the aperture while the rotation inducingand limiting surfaces force the pawl member into a predetermined angularrelationship with the longitudinal axis of the actuator.

3. An alternate action mechanism in accordance with claim 2 wherein thepawl member is of a generally trapezoidal configuration having opposedpairs of adjacent sides with each pair of adjacent sides forming anacute angle A and defining one of said pair of teeth, the uppermostportion of the aperture formed by a pair of camming surfacesintersecting to form an angle substantially equal to acute angle A,wherein the cooperation of the pawl member with the uppermost portion ofthe aperture axially aligns the pawl member in the aperture.

wherein a tooth of the pawl member contacts the ramp surface whichimparts a slight angular rotation to the pawl member and allows theother tooth to abut the first shoulder portion as the actuator is forcedin said first direction and necessitates further movement in theopposite direction to free the pawl. v

5. An alternate action mechanism in accordance with claim 2 wherein thepawl member is shaped as a trapezoid having a pair of short sides and apair of long sides forming a pair of acute included angles and a pair ofobtuse included angles, wherein the acute corners of the pawl definesaid pair of teeth to operatively engage the pocket and shoulderportions in the aperture.

6. An alternate action mechanism in accordance with claim 5 wherein along side of the pawl member cooperates with a side support cammingsurface in the aperture to position the pawl member in axial alignmentwith the actuator when the actuator returns to its initial positionunder the influence of the biasing means.

1. An alternate action mechanism comprising, in combination a hollowcasing, a switch actuator mounted in the casing for straight linereciprocating movement therein, means biasing the actuator in a firstdirection, switch means operatively associated with the actuator, pawlmeans carried for free rotation on the actuator, an aperture in thehollow casing forming camming surfaces and arranged for operativeassociation with the pawl means, said pawl means comprising a pawlmember having a pair of teeth on the opposite ends thereof, the cammingsurfaces comprising pocket and shoulder portions, the pocket portionpositioned to engage one of said teeth when said pawl member is in aninitial position and partially rotate said pawl member responsive tomovement of the actuator in a direction opposite to the bias, theshoulder portion formed and positioned to lockingly engage contiguousopposite sides of the second tooth of said pawl member to preclude thereturn of the actuator to its initial position responsive to saidpartial rotation of said pawl member, a second shoulder portionpositioned to engage said one of said teeth and further rotate said pawlresponsive to a second movement of the actuator in a direction oppositeto the bias, and said camming surfaces including a further surfaceengaging and rotating said pawl member to an initial position responsiveto further movement of the actuator in the direction of said bias.
 2. Analternate action mechanism in accordance with claim 1 wherein thecamming surface is in the form of an aperture in one wall of the hollowcasing and said further surface comprises a side support surfaceextending from the uppermost portion of the aperture in a planegenerally parallel to the plane including the longitudinal axis of theactuator, the pocket portion forming the lowermost extremity of theaperture and including a rotation inducting ramp surface and a rotationlimiting abutment surface wherein the side support surface axiallyaligns the pawl member within the aperture while the rotation inducingand limiting surfaces force the pawl member into a predetermined angularrelationship with the longitudinal axis of the actuator.
 3. An alternateaction mechanism in accordance with claim 2 wherein the pawl member isof a generally trapezoidal configuration having opposed pairs ofadjacent sides with each pair of adjacent sides forming an acute angle Aand defining one of said pair of teeth, the uppermost portion of theaperture formed by a pair of camming surfaces intersecting to form anangle substantially equal to acute angle A, wherein the cooperation ofthe pawl member with the uppermost portion of the aperture axiallyaligns the pawl member in the aperture.
 4. An alternate action mechanismin accordance with claim 3 wherein the rotation inducing ramp surfaceextends at an acute angle B to a plane normal to the axis of movement ofthe actuator, said acute angle B being less than the complement of acuteangle A wherein a tooth of the pawl member contacts the ramp surfacewhich imparts a slight angular rotation to the pawl member and allowsthe other tooth to abut the firSt shoulder portion as the actuator isforced in said first direction and necessitates further movement in theopposite direction to free the pawl.
 5. An alternate action mechanism inaccordance with claim 2 wherein the pawl member is shaped as a trapezoidhaving a pair of short sides and a pair of long sides forming a pair ofacute included angles and a pair of obtuse included angles, wherein theacute corners of the pawl define said pair of teeth to operativelyengage the pocket and shoulder portions in the aperture.
 6. An alternateaction mechanism in accordance with claim 5 wherein a long side of thepawl member cooperates with a side support camming surface in theaperture to position the pawl member in axial alignment with theactuator when the actuator returns to its initial position under theinfluence of the biasing means.